This invention relates to a position sensor, and particularly, to a magneto-strictive sensor for determining a position of a valve in an internal combustion engine.
Automotive manufacturers are currently utilizing camless intake and exhaust valve assemblies to control fluid communication in engine cylinders of internal combustion engines. The camless valve assemblies may utilize hydraulic, pneumatic, or electromechanical means to move a valve.
It is further known that varying an engine valve dwell time (i.e., the time interval a valve is open), a valve dwell position (i.e., the amount the valve is open), a valve opening rate, a valve closing rate, and an initial opening time of a valve (i.e., valve phasing) may be used to increase fuel efficiency and lower emissions. Further, the most flexible valve assemblies may be independently actuated/controlled with respect to other valve assemblies in an engine.
Referring to FIG. 1, a known engine 10 having an engine head 12 and electromechanical valve assemblies 14, 16 is shown. The engine head 12 includes an air intake line 18 and an exhaust line 20. The valve assemblies 14, 16 control communication between the line 18, 20, respectively, with an engine cylinder (not shown).
The valve assembly 14 includes a pair of solenoids 22, 24, and a valve 26. The valve 26 includes a valve stem 28 and a valve head 30. The solenoids 22, 24 are utilized to either open or close the valve 26. In particular, when the solenoid 24 is energized (and solenoid 22 is de-energized), the valve head 30 is moved axially away from a valve seat 32 to allow fluid communication between the intake line 18 and a cylinder (not shown). When the solenoid 22 is energized (and solenoid 24 is de-energized) the valve head 30 engages the valve seat 32 to prevent fluid communication between the intake line 18 and the cylinder. Thus, the known valve assembly 14 has a two-position valve 26 having either a full open state or a full closed state. As such, the valve assembly 14 has several operational disadvantages. In particular, the valve assembly 14 cannot precisely control a valve dwell time duration, a valve dwell position, a valve opening rate, a valve closing rate, valve phasing. Thus, the valve assembly 14 cannot be utilized to effectively increase fuel efficiency and lower emissions in an engine. Further, the valve assembly 14 does not provide for soft seating of the valve head 30 on the valve seat 32 under all operating conditions of the engine 10xe2x80x94including temperature extremes and control strategy variations. As a result, the valve head 30 generates undesirable noise when contacting the valve seat 32.
Another known electromechanical valve assembly (not shown) includes an electric motor, a cam, and a poppet valve. The motor selectively rotates an output shaft that is connected to the cam. The cam converts that rotary motion of the output shaft to an axial motion of the poppet valve. This known valve assembly is capable of controlling a valve dwell time, a valve dwell position, a valve opening rate, and a valve closing rate. However, the known valve assembly suffers from several disadvantages. First, the valve assembly requires a separate cam resulting in increased component and manufacturing costs. Further, the valve assembly requires a relatively large package space since a separate cam is utilized for each poppet valve.
Position sensors have been used to determine an axial position of valves in intake and exhaust valve assemblies. Two commonly used types of position sensors include a Hall Effect sensor and a variable reluctance sensor. Each valve assembly may have a corresponding position sensor disposed on top of the valve assembly. As such, the known position sensors have several disadvantages in an automotive vehicle. In particular, the known position sensors have a relatively thick axial profile. Accordingly, the sensors substantially increase the height of intake and exhaust valve assemblies, resulting in an increased height of a vehicle hood to accommodate the valve assemblies. Those skilled in the art will recognize that a higher vehicle hood results in decreased fuel economy and decreased visual aesthetics of the automotive vehicle.
The present invention provides a magneto-strictive sensor for determining a position of a valve in an electromechanical valve assembly. The electromechanical valve assembly may comprise an intake or exhaust valve assembly in an internal combustion engine.
The magneto-strictive sensor in accordance with the present invention includes two preferred embodiments. The first preferred embodiment of the magneto-strictive sensor is utilized to determine (i) a rotational position of a rotor of an electromechanical valve assembly and (ii) an axial position of a valve of the valve assembly. The rotor includes a sensor magnet attached to the rotor that rotates with the rotor. Accordingly, a rotational position of the sensor magnet is indicative of a rotational position of the rotor. The magneto-strictive sensor includes a sonic conduit extending around a portion of a circumference of the rotor of the valve assembly. The sensor further includes a sonic wave generator generating a sonic wave in the conduit responsive to a transmit signal. The sonic wave propagates to a localized stress boundary in the conduit which is induced by the sensor magnet. The sonic wave is reflected in the conduit from the stress boundary. The sensor further includes a sonic wave receiver receiving the reflected sonic wave from the conduit and generating a received signal responsive to the sonic wave. Finally, the sensor includes a sensor controller configured to generate the transmit signal and to receive the received signal. The controller calculates a position value responsive to a round trip travel time of the sonic wave in the conduit. As previously discussed, the position value represents (i) a rotational position of the rotor and/or (ii) an axial position of the valve.
The second preferred embodiment of the magneto-strictive sensor is utilized to determine an axial position of a valve in a valve assembly. The rotor includes a permanent ring magnet that is stationary along an axial axis of the valve. The magneto-strictive sensor includes a sonic conduit extending generally axially on or integral with the valve. The sensor further includes a sonic wave generator generating a sonic wave in the conduit responsive to a transmit signal. The sonic wave propagates to a localized stress boundary in the conduit. The stress boundary is induced by the ring magnet and the sonic wave is reflected in the conduit from the boundary. The sensor further includes a sonic wave receiver receiving the reflected sonic wave and generating a received signal responsive to the sonic wave. Finally, the sensor includes a sensor controller configured to generate the transmit signal and to receive the received signal. The controller calculates a position value responsive to a round trip travel time of the sonic wave in said conduit. As previously discussed, the position value represents an axial position value of the valve.
The magneto-strictive sensor in accordance with the present invention represents a significant improvement over conventional position sensors. In particular, the inventive sensor has an extremely thin axial profile as compared with conventional sensors. Accordingly, the inventive sensor may be disposed within a valve enclosure without increasing the height of an intake or exhaust valve assembly. Accordingly, the lower valve assemblies allow for a lower vehicle hood profile that results in increased fuel economy of the automotive vehicle.
These and other features and advantages of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.